# Objective
Fixes#7736
## Solution
Implement the `SystemParam` trait for `WorldId`
## Changelog
- `WorldId` can now be taken as a system parameter and will return the id of the world the system is running in
# Objective
- Fixes#7659.
## Solution
- This PR extracted the `distributive_run_if` part of #7676, because it does not require the controversial introduction of anonymous system sets.
- The distinctive name should make the user aware about the differences between `IntoSystemConfig::run_if` and `IntoSystemConfigs::distributive_run_if`.
- The documentation explains in detail the consequences of using the API and possible pit falls when using it.
- A test demonstrates the possibility of changing the condition result, resulting in some of the systems not being run.
---
## Changelog
### Added
- Add `distributive_run_if` to `IntoSystemConfigs` to enable adding a run condition to each system when using `add_systems`.
follow-up to https://github.com/bevyengine/bevy/pull/7716
# Objective
System access is only populated in `System::initialize`, so without calling `initialize` it's actually impossible to see most ambiguities.
## Solution
- make `initialize` public. The method is idempotent, so calling it multiple times doesn't hurt
# Objective
Continuation of https://github.com/bevyengine/bevy/pull/5719
Now that we have a definable type for the iterator.
---
## Changelog
- Implemented IntoIterator for EventReader so you can now do `&mut reader` instead of `reader.iter()` for events.
# Objective
Fix#7440. Fix#7441.
## Solution
* Remove builder functions on `ScheduleBuildSettings` in favor of public fields, move docs to the fields.
* Add `use_shortnames` and use it in `get_node_name` to feed it through `bevy_utils::get_short_name`.
# Objective
Web builds do not support running on multiple threads right now. Defaulting to the multi-threaded executor has significant overhead without any benefit.
## Solution
Default to the single threaded executor on wasm32 builds.
# Objective
- other tools (bevy_mod_debugdump) would like to have access to the ambiguities so that they can do their own reporting/visualization
## Solution
- store `conflicting_systems` in `ScheduleGraph` after calling `build_schedule`
The solution isn't very pretty and as pointed out it https://github.com/bevyengine/bevy/pull/7522, there may be a better way of exposing this, but this is the quick and dirty way if we want to have this functionality exposed in 0.10.
# Objective
- RemovedComponents is just a thin wrapper around Events/ManualEventReader which is the same as an EventReader, so most usecases that of an EventReader will probably be useful for RemovedComponents too.
I was thinking of making a trait for this but I don't think it is worth the overhead currently.
## Solution
- Mirror the api surface of EventReader
# Objective
Motivated by #7469.
`EventReader` iterators use the default implementations for `.nth()` and `.last()`, which includes iterating over and throwing out all events before the desired one.
## Solution
Add specialized implementations for these methods that directly updates the unread event counter and returns a reference to the desired event.
TODO:
- [x] Add a unit test.
- [x] ~~Add a benchmark, to see if the compiler was doing this automatically already.~~ *On second thought, this doesn't feel like a very useful thing to include in the benchmark suite.*
# Objective
- it would be nice to be able to associate a `NodeId` of a system type set to the `NodeId` of the actual system (used in bevy_mod_debugdump)
## Solution
- make `system_type` return the type id of the system
- that way you can check if a `dyn SystemSet` is the system type set of a `dyn System`
- I don't know if this information is already present somewhere else in the scheduler or if there is a better way to expose it
# Objective
Fixes#7702.
## Solution
- Added an test that ensures that no error is returned if a system or set is inside two different sets that share the same base set.
- Added an check to only return an error if the two base sets are not equal.
# Objective
The `ScheduleGraph` should be expose so that crates like [bevy_mod_debugdump](https://github.com/jakobhellermann/bevy_mod_debugdump/blob/stageless/docs/README.md) can access useful information.
## Solution
- expose `ScheduleGraph`, `NodeId`, `BaseSetMembership`, `Dag`
- add accessor functions for sets and systems
## Changelog
- expose `ScheduleGraph` for use in third party tools
This does expose our use of `petgraph` as a graph library, so we can only change that as a breaking change.
# Objective
- Fixes#5432
- Fixes#6680
## Solution
- move code responsible for generating the `impl TypeUuid` from `type_uuid_derive` into a new function, `gen_impl_type_uuid`.
- this allows the new proc macro, `impl_type_uuid`, to call the code for generation.
- added struct `TypeUuidDef` and implemented `syn::Parse` to allow parsing of the input for the new macro.
- finally, used the new macro `impl_type_uuid` to implement `TypeUuid` for the standard library (in `crates/bevy_reflect/src/type_uuid_impl.rs`).
- fixes#6680 by doing a wrapping add of the param's index to its `TYPE_UUID`
Co-authored-by: dis-da-moe <84386186+dis-da-moe@users.noreply.github.com>
# Objective
The trait `Condition<>` is implemented for any type that can be converted into a `ReadOnlySystem` which takes no inputs and returns a bool. However, due to the current implementation, consumers of the trait cannot rely on the fact that `<T as Condition>::System` implements `ReadOnlySystem`. In cases such as the `not` combinator (added in #7559), we are required to add redundant `T::System: ReadOnlySystem` trait bounds, even though this should be implied by the `Condition<>` trait.
## Solution
Add a hidden associated type which allows the compiler to figure out that the `System` associated type implements `ReadOnlySystem`.
…able like Table. Rename clear to clear_entities to clarify that metadata keeps, only value cleared
# Objective
- Provide some inspectability for SparseSets.
## Solution
- `Tables` has these three methods, len, is_empty and iter too. Add these methods to `SparseSets`, so user can print the shape of storage.
---
## Changelog
> This section is optional. If this was a trivial fix, or has no externally-visible impact, you can delete this section.
- Add `len`, `is_empty`, `iter` methods on SparseSets.
- Rename `clear` to `clear_entities` to clarify its purpose.
- Add `new_for_test` on `ComponentInfo` to make test code easy.
- Add test case covering new methods.
## Migration Guide
> This section is optional. If there are no breaking changes, you can delete this section.
- Simply adding new functionality is not a breaking change.
# Objective
This PR improves message that caused by duplicate components in bundle.
## Solution
Show names of duplicate components.
The solution is not very elegant, in my opinion, I will be happy to listen to suggestions for improving it
Co-authored-by: Саня Череп <41489405+SDesya74@users.noreply.github.com>
# Objective
While porting my crate `bevy_trait_query` to bevy 0.10, I ran into an issue with the `DetectChangesMut` trait. Due to the way that the `set_if_neq` method (added in #6853) is implemented, you are forced to write a nonsense implementation of it for dynamically sized types. This edge case shows up when implementing trait queries, since `DetectChangesMut` is implemented for `Mut<dyn Trait>`.
## Solution
Simplify the generics for `set_if_neq` and add the `where Self::Target: Sized` trait bound to it. Add a default implementation so implementers don't need to implement a method with nonsensical trait bounds.
# Objective
The `SystemParamFunction` (and `ExclusiveSystemParamFunction`) trait is very cumbersome to use, due to it requiring four generic type parameters. These are currently all used as marker parameters to satisfy rust's trait coherence rules.
### Example (before)
```rust
pub fn pipe<AIn, Shared, BOut, A, AParam, AMarker, B, BParam, BMarker>(
mut system_a: A,
mut system_b: B,
) -> impl FnMut(In<AIn>, ParamSet<(AParam, BParam)>) -> BOut
where
A: SystemParamFunction<AIn, Shared, AParam, AMarker>,
B: SystemParamFunction<Shared, BOut, BParam, BMarker>,
AParam: SystemParam,
BParam: SystemParam,
```
## Solution
Turn the `In`, `Out`, and `Param` generics into associated types. Merge the marker types together to retain coherence.
### Example (after)
```rust
pub fn pipe<A, B, AMarker, BMarker>(
mut system_a: A,
mut system_b: B,
) -> impl FnMut(In<A::In>, ParamSet<(A::Param, B::Param)>) -> B::Out
where
A: SystemParamFunction<AMarker>,
B: SystemParamFunction<BMarker, In = A::Out>,
```
---
## Changelog
+ Simplified the `SystemParamFunction` and `ExclusiveSystemParamFunction` traits.
## Migration Guide
For users of the `SystemParamFunction` trait, the generic type parameters `In`, `Out`, and `Param` have been turned into associated types. The same has been done with the `ExclusiveSystemParamFunction` trait.
# Objective
- #6402 changed `World::fetch_table` (now `UnsafeWorldCell::fetch_table`) to access the archetype in order to get the `table_id` and `table_row` of the entity involved. However this is useless since those were already present in the `EntityLocation`
- Moreover it's useless for `UnsafeWorldCell::fetch_table` to return the `TableRow` too, since the caller must already have access to the `EntityLocation` which contains the `TableRow`.
- The result is that `UnsafeWorldCell::fetch_table` now only does 2 memory fetches instead of 4.
## Solution
- Revert the changes to the implementation of `UnsafeWorldCell::fetch_table` made in #6402
…u64, so hash safety is not a concern
# Objective
- While reading the code, just noticed the BundleInfo's HashMap is std::collections::HashMap, which uses a slow but safe hasher.
## Solution
- Use bevy_utils::HashMap instead
benchmark diff (I run several times in a linux box, the perf improvement is consistent, though numbers varies from time to time, I paste my last run result here):
``` bash
cargo bench -- spawn
Compiling bevy_ecs v0.9.0 (/home/lishuo/developer/pr/bevy/crates/bevy_ecs)
Compiling bevy_app v0.9.0 (/home/lishuo/developer/pr/bevy/crates/bevy_app)
Compiling benches v0.1.0 (/home/lishuo/developer/pr/bevy/benches)
Finished bench [optimized] target(s) in 1m 17s
Running benches/bevy_ecs/change_detection.rs (/home/lishuo/developer/pr/bevy/benches/target/release/deps/change_detection-86c5445d0dc34529)
Gnuplot not found, using plotters backend
Running benches/bevy_ecs/benches.rs (/home/lishuo/developer/pr/bevy/benches/target/release/deps/ecs-e49b3abe80bfd8c0)
Gnuplot not found, using plotters backend
spawn_commands/2000_entities
time: [153.94 µs 159.19 µs 164.37 µs]
change: [-14.706% -11.050% -6.9633%] (p = 0.00 < 0.05)
Performance has improved.
spawn_commands/4000_entities
time: [328.77 µs 339.11 µs 349.11 µs]
change: [-7.6331% -3.9932% +0.0487%] (p = 0.06 > 0.05)
No change in performance detected.
spawn_commands/6000_entities
time: [445.01 µs 461.29 µs 477.36 µs]
change: [-16.639% -13.358% -10.006%] (p = 0.00 < 0.05)
Performance has improved.
spawn_commands/8000_entities
time: [657.94 µs 677.71 µs 696.95 µs]
change: [-8.8708% -5.2591% -1.6847%] (p = 0.01 < 0.05)
Performance has improved.
get_or_spawn/individual time: [452.02 µs 466.70 µs 482.07 µs]
change: [-17.218% -14.041% -10.728%] (p = 0.00 < 0.05)
Performance has improved.
get_or_spawn/batched time: [291.12 µs 301.12 µs 311.31 µs]
change: [-12.281% -8.9163% -5.3660%] (p = 0.00 < 0.05)
Performance has improved.
spawn_world/1_entities time: [81.668 ns 84.284 ns 86.860 ns]
change: [-12.251% -6.7872% -1.5402%] (p = 0.02 < 0.05)
Performance has improved.
spawn_world/10_entities time: [789.78 ns 821.96 ns 851.95 ns]
change: [-19.738% -14.186% -8.0733%] (p = 0.00 < 0.05)
Performance has improved.
spawn_world/100_entities
time: [7.9906 µs 8.2449 µs 8.5013 µs]
change: [-12.417% -6.6837% -0.8766%] (p = 0.02 < 0.05)
Change within noise threshold.
spawn_world/1000_entities
time: [81.602 µs 84.161 µs 86.833 µs]
change: [-13.656% -8.6520% -3.0491%] (p = 0.00 < 0.05)
Performance has improved.
Found 1 outliers among 100 measurements (1.00%)
1 (1.00%) high mild
Benchmarking spawn_world/10000_entities: Warming up for 500.00 ms
Warning: Unable to complete 100 samples in 4.0s. You may wish to increase target time to 4.0s, enable flat sampling, or reduce sample count to 70.
spawn_world/10000_entities
time: [813.02 µs 839.76 µs 865.41 µs]
change: [-12.133% -6.1970% -0.2302%] (p = 0.05 < 0.05)
Change within noise threshold.
```
---
## Changelog
> This section is optional. If this was a trivial fix, or has no externally-visible impact, you can delete this section.
- use bevy_utils::HashMap for Bundles::bundle_ids
## Migration Guide
> This section is optional. If there are no breaking changes, you can delete this section.
- Not a breaking change, hashmap is internal impl.
# Objective
We have a few old system labels that are now system sets but are still named or documented as labels. Documentation also generally mentioned system labels in some places.
## Solution
- Clean up naming and documentation regarding system sets
## Migration Guide
`PrepareAssetLabel` is now called `PrepareAssetSet`
# Objective
- Improve readability of the run condition for systems only running in a certain state
## Solution
- Rename `state_equals` to `in_state` (see [comment by cart](https://github.com/bevyengine/bevy/pull/7634#issuecomment-1428740311) in #7634 )
- `.run_if(state_equals(variant))` now is `.run_if(in_state(variant))`
This breaks the naming pattern a bit with the related conditions `state_exists` and `state_exists_and_equals` but I could not think of better names for those and think the improved readability of `in_state` is worth it.
# Objective
Fixes#7632.
As discussed in #7634, it can be quite challenging for users to intuit the mental model of how states now work.
## Solution
Rather than change the behavior of the `OnUpdate` system set, instead work on making sure it's easy to understand what's going on.
Two things have been done:
1. Remove the `.on_update` method from our bevy of system building traits. This was special-cased and made states feel much more magical than they need to.
2. Improve the docs for the `OnUpdate` system set.
# Objective
- Fixes: #7187
Since avoiding the `SRes::into_inner` call does not seem to be possible, this PR tries to at least document its usage.
I am not sure if I explained the lifetime issue correctly, please let me know if something is incorrect.
## Solution
- Add information about the `SRes::into_inner` usage on both `RenderCommand` and `Res`
# Objective
Related to #7530.
`EventReader` iterators currently use the default impl for `.count()`, which unnecessarily loops over all unread events.
# Solution
Add specialized impls that mark the `EventReader` as consumed and return the number of unread events.
# Objective
Make the name less verbose without sacrificing clarity.
---
## Migration Guide
*Note for maintainers:* This PR has no breaking changes relative to bevy 0.9. Instead of this PR having its own migration guide, we should just edit the changelog for #6404.
The type `UnsafeWorldCellEntityRef` has been renamed to `UnsafeEntityCell`.
# Objective
Continuation of #7560.
`MutUntyped::last_changed` and `set_last_changed` do not behave as described in their docs.
## Solution
Fix them using the same approach that was used for `Mut<>` in #7560.
# Objective
Make `last_changed` behave as described in its docs.
## Solution
- Return `changed` instead of `last_change_tick`. `last_change_tick` is the system's previous tick and is just used for comparison.
- Update the docs of the similarly named `set_last_changed` (which does correctly interact with `last_change_tick`) to clarify that the two functions touch different data. (I advocate for renaming one or the other if anyone has any good suggestions).
It also might make sense to return a cloned `Tick` instead of `u32`.
---
## Changelog
- Fixed `DetectChanges::last_changed` returning the wrong value.
- Fixed `DetectChangesMut::set_last_changed` not actually updating the `changed` tick.
## Migration Guide
- The incorrect value that was being returned by `DetectChanges::last_changed` was the previous run tick of the system checking for changed values. If you depended on this value, you can get it from the `SystemChangeTick` `SystemParam` instead.
# Objective
Clarify what the function is actually calculating.
The `Tick::is_older_than` function is actually calculating whether the tick is newer than the system's `last_change_tick`, not older. As far as I can tell, the engine was using it correctly everywhere already.
## Solution
- Rename the function.
---
## Changelog
- `Tick::is_older_than` was renamed to `Tick::is_newer_than`. This is not a functional change, since that was what was always being calculated, despite the wrong name.
## Migration Guide
- Replace usages of `Tick::is_older_than` with `Tick::is_newer_than`.
# Objective
Closes#7202
## Solution
~~Introduce a `not` helper to pipe conditions. Opened mostly for discussion. Maybe create an extension trait with `not` method? Please, advice.~~
Introduce `not(condition)` condition that inverses the result of the passed.
---
## Changelog
### Added
- `not` condition.
Small commit to remove an unused resource scoped within a single bevy_ecs unit test. Also rearranged the initialization to follow initialization conventions of surrounding tests. World/Schedule initialization followed by resource initialization.
This change was tested locally with `cargo test`, and `cargo fmt` was run.
Risk should be tiny as change is scoped to a single unit test and very tiny, and I can't see any way that this resource is being used in the test.
Thank you so much!
# Objective
Run conditions are a special type of system that do not modify the world, and which return a bool. Due to the way they are currently implemented, you can *only* use bare function systems as a run condition. Among other things, this prevents the use of system piping with run conditions. This make very basic constructs impossible, such as `my_system.run_if(my_condition.pipe(not))`.
Unblocks a basic solution for #7202.
## Solution
Add the trait `ReadOnlySystem`, which is implemented for any system whose parameters all implement `ReadOnlySystemParam`. Allow any `-> bool` system implementing this trait to be used as a run condition.
---
## Changelog
+ Added the trait `ReadOnlySystem`, which is implemented for any `System` type whose parameters all implement `ReadOnlySystemParam`.
+ Added the function `bevy::ecs::system::assert_is_read_only_system`.
# Objective
Implementing `States` manually is repetitive, so let's not.
One thing I'm unsure of is whether the macro import statement is in the right place.
# Objective
One pattern to increase parallelism is deferred mutation: instead of directly mutating the world (and preventing other systems from running at the same time), you queue up operations to be applied to the world at the end of the stage. The most common example of this pattern uses the `Commands` SystemParam.
In order to avoid the overhead associated with commands, some power users may want to add their own deferred mutation behavior. To do this, you must implement the unsafe trait `SystemParam`, which interfaces with engine internals in a way that we'd like users to be able to avoid.
## Solution
Add the `Deferred<T>` primitive `SystemParam`, which encapsulates the deferred mutation pattern.
This can be combined with other types of `SystemParam` to safely and ergonomically create powerful custom types.
Essentially, this is just a variant of `Local<T>` which can run code at the end of the stage.
This type is used in the engine to derive `Commands` and `ParallelCommands`, which removes a bunch of unsafe boilerplate.
### Example
```rust
use bevy_ecs::system::{Deferred, SystemBuffer};
/// Sends events with a delay, but may run in parallel with other event writers.
#[derive(SystemParam)]
pub struct BufferedEventWriter<'s, E: Event> {
queue: Deferred<'s, EventQueue<E>>,
}
struct EventQueue<E>(Vec<E>);
impl<'s, E: Event> BufferedEventWriter<'s, E> {
/// Queues up an event to be sent at the end of this stage.
pub fn send(&mut self, event: E) {
self.queue.0.push(event);
}
}
// The `SystemBuffer` trait controls how [`Deferred`] gets applied at the end of the stage.
impl<E: Event> SystemBuffer for EventQueue<E> {
fn apply(&mut self, world: &mut World) {
let mut events = world.resource_mut::<Events<E>>();
for e in self.0.drain(..) {
events.send(e);
}
}
}
```
---
## Changelog
+ Added the `SystemParam` type `Deferred<T>`, which can be used to defer `World` mutations. Powered by the new trait `SystemBuffer`.
# Objective
- There is a small perf cost for starting the multithreaded executor.
## Solution
- We can skip that cost when there are zero systems in the schedule. Overall not a big perf boost unless there are a lot of empty schedules that are trying to run, but it is something.
Below is a tracy trace of the run_fixed_update_schedule for many_foxes which has zero systems in it. Yellow is main and red is this pr. The time difference between the peaks of the humps is around 15us.
# Objective
- Implementing logic used by system params and `UnsafeWorldCell` on `&World` is sus since `&World` generally denotes shared read only access to world but this is a lie in the above situations. Move most/all logic that uses `&World` to mean `UnsafeWorldCell` onto `UnsafeWorldCell`
- Add a way to take a `&mut World` out of `UnsafeWorldCell` and use this in `WorldCell`'s `Drop` impl instead of a `UnsafeCell` field
---
## Changelog
- changed some `UnsafeWorldCell` methods to take `self` instead of `&self`/`&mut self` since there is literally no point to them doing that
- `UnsafeWorldCell::world` is now used to get immutable access to the whole world instead of just the metadata which can now be done via `UnsafeWorldCell::world_metadata`
- `UnsafeWorldCell::world_mut` now exists and can be used to get a `&mut World` out of `UnsafeWorldCell`
- removed `UnsafeWorldCell::storages` since that is probably unsound since storages contains the actual component/resource data not just metadata
## Migration guide
N/A none of the breaking changes here make any difference for a 0.9->0.10 transition since `UnsafeWorldCell` did not exist in 0.9
# Objective
NOTE: This depends on #7267 and should not be merged until #7267 is merged. If you are reviewing this before that is merged, I highly recommend viewing the Base Sets commit instead of trying to find my changes amongst those from #7267.
"Default sets" as described by the [Stageless RFC](https://github.com/bevyengine/rfcs/pull/45) have some [unfortunate consequences](https://github.com/bevyengine/bevy/discussions/7365).
## Solution
This adds "base sets" as a variant of `SystemSet`:
A set is a "base set" if `SystemSet::is_base` returns `true`. Typically this will be opted-in to using the `SystemSet` derive:
```rust
#[derive(SystemSet, Clone, Hash, Debug, PartialEq, Eq)]
#[system_set(base)]
enum MyBaseSet {
A,
B,
}
```
**Base sets are exclusive**: a system can belong to at most one "base set". Adding a system to more than one will result in an error. When possible we fail immediately during system-config-time with a nice file + line number. For the more nested graph-ey cases, this will fail at the final schedule build.
**Base sets cannot belong to other sets**: this is where the word "base" comes from
Systems and Sets can only be added to base sets using `in_base_set`. Calling `in_set` with a base set will fail. As will calling `in_base_set` with a normal set.
```rust
app.add_system(foo.in_base_set(MyBaseSet::A))
// X must be a normal set ... base sets cannot be added to base sets
.configure_set(X.in_base_set(MyBaseSet::A))
```
Base sets can still be configured like normal sets:
```rust
app.add_system(MyBaseSet::B.after(MyBaseSet::Ap))
```
The primary use case for base sets is enabling a "default base set":
```rust
schedule.set_default_base_set(CoreSet::Update)
// this will belong to CoreSet::Update by default
.add_system(foo)
// this will override the default base set with PostUpdate
.add_system(bar.in_base_set(CoreSet::PostUpdate))
```
This allows us to build apis that work by default in the standard Bevy style. This is a rough analog to the "default stage" model, but it use the new "stageless sets" model instead, with all of the ordering flexibility (including exclusive systems) that it provides.
---
## Changelog
- Added "base sets" and ported CoreSet to use them.
## Migration Guide
TODO
Huge thanks to @maniwani, @devil-ira, @hymm, @cart, @superdump and @jakobhellermann for the help with this PR.
# Objective
- Followup #6587.
- Minimal integration for the Stageless Scheduling RFC: https://github.com/bevyengine/rfcs/pull/45
## Solution
- [x] Remove old scheduling module
- [x] Migrate new methods to no longer use extension methods
- [x] Fix compiler errors
- [x] Fix benchmarks
- [x] Fix examples
- [x] Fix docs
- [x] Fix tests
## Changelog
### Added
- a large number of methods on `App` to work with schedules ergonomically
- the `CoreSchedule` enum
- `App::add_extract_system` via the `RenderingAppExtension` trait extension method
- the private `prepare_view_uniforms` system now has a public system set for scheduling purposes, called `ViewSet::PrepareUniforms`
### Removed
- stages, and all code that mentions stages
- states have been dramatically simplified, and no longer use a stack
- `RunCriteriaLabel`
- `AsSystemLabel` trait
- `on_hierarchy_reports_enabled` run criteria (now just uses an ad hoc resource checking run condition)
- systems in `RenderSet/Stage::Extract` no longer warn when they do not read data from the main world
- `RunCriteriaLabel`
- `transform_propagate_system_set`: this was a nonstandard pattern that didn't actually provide enough control. The systems are already `pub`: the docs have been updated to ensure that the third-party usage is clear.
### Changed
- `System::default_labels` is now `System::default_system_sets`.
- `App::add_default_labels` is now `App::add_default_sets`
- `CoreStage` and `StartupStage` enums are now `CoreSet` and `StartupSet`
- `App::add_system_set` was renamed to `App::add_systems`
- The `StartupSchedule` label is now defined as part of the `CoreSchedules` enum
- `.label(SystemLabel)` is now referred to as `.in_set(SystemSet)`
- `SystemLabel` trait was replaced by `SystemSet`
- `SystemTypeIdLabel<T>` was replaced by `SystemSetType<T>`
- The `ReportHierarchyIssue` resource now has a public constructor (`new`), and implements `PartialEq`
- Fixed time steps now use a schedule (`CoreSchedule::FixedTimeStep`) rather than a run criteria.
- Adding rendering extraction systems now panics rather than silently failing if no subapp with the `RenderApp` label is found.
- the `calculate_bounds` system, with the `CalculateBounds` label, is now in `CoreSet::Update`, rather than in `CoreSet::PostUpdate` before commands are applied.
- `SceneSpawnerSystem` now runs under `CoreSet::Update`, rather than `CoreStage::PreUpdate.at_end()`.
- `bevy_pbr::add_clusters` is no longer an exclusive system
- the top level `bevy_ecs::schedule` module was replaced with `bevy_ecs::scheduling`
- `tick_global_task_pools_on_main_thread` is no longer run as an exclusive system. Instead, it has been replaced by `tick_global_task_pools`, which uses a `NonSend` resource to force running on the main thread.
## Migration Guide
- Calls to `.label(MyLabel)` should be replaced with `.in_set(MySet)`
- Stages have been removed. Replace these with system sets, and then add command flushes using the `apply_system_buffers` exclusive system where needed.
- The `CoreStage`, `StartupStage, `RenderStage` and `AssetStage` enums have been replaced with `CoreSet`, `StartupSet, `RenderSet` and `AssetSet`. The same scheduling guarantees have been preserved.
- Systems are no longer added to `CoreSet::Update` by default. Add systems manually if this behavior is needed, although you should consider adding your game logic systems to `CoreSchedule::FixedTimestep` instead for more reliable framerate-independent behavior.
- Similarly, startup systems are no longer part of `StartupSet::Startup` by default. In most cases, this won't matter to you.
- For example, `add_system_to_stage(CoreStage::PostUpdate, my_system)` should be replaced with
- `add_system(my_system.in_set(CoreSet::PostUpdate)`
- When testing systems or otherwise running them in a headless fashion, simply construct and run a schedule using `Schedule::new()` and `World::run_schedule` rather than constructing stages
- Run criteria have been renamed to run conditions. These can now be combined with each other and with states.
- Looping run criteria and state stacks have been removed. Use an exclusive system that runs a schedule if you need this level of control over system control flow.
- For app-level control flow over which schedules get run when (such as for rollback networking), create your own schedule and insert it under the `CoreSchedule::Outer` label.
- Fixed timesteps are now evaluated in a schedule, rather than controlled via run criteria. The `run_fixed_timestep` system runs this schedule between `CoreSet::First` and `CoreSet::PreUpdate` by default.
- Command flush points introduced by `AssetStage` have been removed. If you were relying on these, add them back manually.
- Adding extract systems is now typically done directly on the main app. Make sure the `RenderingAppExtension` trait is in scope, then call `app.add_extract_system(my_system)`.
- the `calculate_bounds` system, with the `CalculateBounds` label, is now in `CoreSet::Update`, rather than in `CoreSet::PostUpdate` before commands are applied. You may need to order your movement systems to occur before this system in order to avoid system order ambiguities in culling behavior.
- the `RenderLabel` `AppLabel` was renamed to `RenderApp` for clarity
- `App::add_state` now takes 0 arguments: the starting state is set based on the `Default` impl.
- Instead of creating `SystemSet` containers for systems that run in stages, simply use `.on_enter::<State::Variant>()` or its `on_exit` or `on_update` siblings.
- `SystemLabel` derives should be replaced with `SystemSet`. You will also need to add the `Debug`, `PartialEq`, `Eq`, and `Hash` traits to satisfy the new trait bounds.
- `with_run_criteria` has been renamed to `run_if`. Run criteria have been renamed to run conditions for clarity, and should now simply return a bool.
- States have been dramatically simplified: there is no longer a "state stack". To queue a transition to the next state, call `NextState::set`
## TODO
- [x] remove dead methods on App and World
- [x] add `App::add_system_to_schedule` and `App::add_systems_to_schedule`
- [x] avoid adding the default system set at inappropriate times
- [x] remove any accidental cycles in the default plugins schedule
- [x] migrate benchmarks
- [x] expose explicit labels for the built-in command flush points
- [x] migrate engine code
- [x] remove all mentions of stages from the docs
- [x] verify docs for States
- [x] fix uses of exclusive systems that use .end / .at_start / .before_commands
- [x] migrate RenderStage and AssetStage
- [x] migrate examples
- [x] ensure that transform propagation is exported in a sufficiently public way (the systems are already pub)
- [x] ensure that on_enter schedules are run at least once before the main app
- [x] re-enable opt-in to execution order ambiguities
- [x] revert change to `update_bounds` to ensure it runs in `PostUpdate`
- [x] test all examples
- [x] unbreak directional lights
- [x] unbreak shadows (see 3d_scene, 3d_shape, lighting, transparaency_3d examples)
- [x] game menu example shows loading screen and menu simultaneously
- [x] display settings menu is a blank screen
- [x] `without_winit` example panics
- [x] ensure all tests pass
- [x] SubApp doc test fails
- [x] runs_spawn_local tasks fails
- [x] [Fix panic_when_hierachy_cycle test hanging](https://github.com/alice-i-cecile/bevy/pull/120)
## Points of Difficulty and Controversy
**Reviewers, please give feedback on these and look closely**
1. Default sets, from the RFC, have been removed. These added a tremendous amount of implicit complexity and result in hard to debug scheduling errors. They're going to be tackled in the form of "base sets" by @cart in a followup.
2. The outer schedule controls which schedule is run when `App::update` is called.
3. I implemented `Label for `Box<dyn Label>` for our label types. This enables us to store schedule labels in concrete form, and then later run them. I ran into the same set of problems when working with one-shot systems. We've previously investigated this pattern in depth, and it does not appear to lead to extra indirection with nested boxes.
4. `SubApp::update` simply runs the default schedule once. This sucks, but this whole API is incomplete and this was the minimal changeset.
5. `time_system` and `tick_global_task_pools_on_main_thread` no longer use exclusive systems to attempt to force scheduling order
6. Implemetnation strategy for fixed timesteps
7. `AssetStage` was migrated to `AssetSet` without reintroducing command flush points. These did not appear to be used, and it's nice to remove these bottlenecks.
8. Migration of `bevy_render/lib.rs` and pipelined rendering. The logic here is unusually tricky, as we have complex scheduling requirements.
## Future Work (ideally before 0.10)
- Rename schedule_v3 module to schedule or scheduling
- Add a derive macro to states, and likely a `EnumIter` trait of some form
- Figure out what exactly to do with the "systems added should basically work by default" problem
- Improve ergonomics for working with fixed timesteps and states
- Polish FixedTime API to match Time
- Rebase and merge #7415
- Resolve all internal ambiguities (blocked on better tools, especially #7442)
- Add "base sets" to replace the removed default sets.
# Objective
- Currently exclusive systems and applying buffers run outside of the multithreaded executor and just calls the funtions on the thread the schedule is running on. Stageless changes this to run these using tasks in a scope. Specifically It uses `spawn_on_scope` to run these. For the render thread this is incorrect as calling `spawn_on_scope` there runs tasks on the main thread. It should instead run these on the render thread and only run nonsend systems on the main thread.
## Solution
- Add another executor to `Scope` for spawning tasks on the scope. `spawn_on_scope` now always runs the task on the thread the scope is running on. `spawn_on_external` spawns onto the external executor than is optionally passed in. If None is passed `spawn_on_external` will spawn onto the scope executor.
- Eventually this new machinery will be able to be removed. This will happen once a fix for removing NonSend resources from the world lands. So this is a temporary fix to support stageless.
---
## Changelog
- add a spawn_on_external method to allow spawning on the scope's thread or an external thread
## Migration Guide
> No migration guide. The main thread executor was introduced in pipelined rendering which was merged for 0.10. spawn_on_scope now behaves the same way as on 0.9.
# Objective
- Make the internals of `RemovedComponents` clearer
## Solution
- Add a wrapper around `Entity`, used in `RemovedComponents` as `Events<RemovedComponentsEntity>`
---
## Changelog
- `RemovedComponents` now internally uses an `Events<RemovedComponentsEntity>` instead of an `Events<Entity>`
The `DoubleEndedIterator` impls produce incorrect results on subsequent calls to `iter()` if the iterator is only partially consumed.
The following code shows what happens
```rust
fn next_back_is_bad() {
let mut events = Events::<TestEvent>::default();
events.send(TestEvent { i: 0 });
events.send(TestEvent { i: 1 });
events.send(TestEvent { i: 2 });
let mut reader = events.get_reader();
let mut iter = reader.iter(&events);
assert_eq!(iter.next_back(), Some(&TestEvent { i: 2 }));
assert_eq!(iter.next(), Some(&TestEvent { i: 0 }));
let mut iter = reader.iter(&events);
// `i: 2` event is returned twice! The `i: 1` event is missed.
assert_eq!(iter.next(), Some(&TestEvent { i: 2 }));
assert_eq!(iter.next(), None);
}
```
I don't think this can be fixed without adding some very convoluted bookkeeping.
## Migration Guide
`ManualEventIterator` and `ManualEventIteratorWithId` are no longer `DoubleEndedIterator`s.
Co-authored-by: devil-ira <justthecooldude@gmail.com>
# Objective
Removal events are unwieldy and require some knowledge of when to put systems that need to catch events for them, it is very easy to end up missing one and end up with memory leak-ish issues where you don't clean up after yourself.
## Solution
Consolidate removals with the benefits of `Events<...>` (such as double buffering and per system ticks for reading the events) and reduce the special casing of it, ideally I was hoping to move the removals to a `Resource` in the world, but that seems a bit more rough to implement/maintain because of double mutable borrowing issues.
This doesn't go the full length of change detection esque removal detection a la https://github.com/bevyengine/rfcs/pull/44.
Just tries to make the current workflow a bit more user friendly so detecting removals isn't such a scheduling nightmare.
---
## Changelog
- RemovedComponents<T> is now backed by an `Events<Entity>` for the benefits of double buffering.
## Migration Guide
- Add a `mut` for `removed: RemovedComponents<T>` since we are now modifying an event reader internally.
- Iterating over removed components now requires `&mut removed_components` or `removed_components.iter()` instead of `&removed_components`.
# Objective
The trait method `SystemParam::apply` allows a `SystemParam` type to defer world mutations, which is internally used to apply `Commands` at the end of the stage. Any operations that require `&mut World` access must be deferred in this way, since parallel systems do not have exclusive access to the world.
The `ExclusiveSystemParam` trait (added in #6083) has an `apply` method which serves the same purpose. However, deferring mutations in this way does not make sense for exclusive systems since they already have `&mut World` access: there is no need to wait until a hard sync point, as the system *is* a hard sync point. World mutations can and should be performed within the body of the system.
## Solution
Remove the method. There were no implementations of this method in the engine.
---
## Changelog
*Note for maintainers: this changelog makes more sense if it's placed above the one for #6919.*
- Removed the method `ExclusiveSystemParamState::apply`.
## Migration Guide
*Note for maintainers: this migration guide makes more sense if it's placed above the one for #6919.*
The trait method `ExclusiveSystemParamState::apply` has been removed. If you have an exclusive system with buffers that must be applied, you should apply them within the body of the exclusive system.
# Objective
Fixes#7434.
This is my first time contributing to a Rust project, so please let me know if this wasn't the change intended by the linked issue.
## Solution
Adds a test with a system that panics to `bevy_ecs`.
I'm not sure if this is the intended panic message, but this is what the test currently results in:
```
thread 'system::tests::panic_inside_system' panicked at 'called `Option::unwrap()` on a `None` value', /Users/bjorn/workplace/bevy/crates/bevy_tasks/src/task_pool.rs:354:49
```
# Objective
Fix#7447.
The `SystemParam` derive uses the wrong lifetimes for ignored fields.
## Solution
Use type inference instead of explicitly naming the types of ignored fields. This allows the compiler to automatically use the correct lifetime.
